1. Field of Invention
This invention relates to a method and apparatus for reliability evaluation and performance analysis of an Internet Protocol (IP) backbone network.
2. Description of Related Art
Currently, in a circuit-switched network, which is connection-oriented, the reliability of the network is measured based on the reliability of T1/T3 circuits, i.e., the percentage that a T1/T3 circuit is fully connected. When a network component fails in the circuit-switched network, it will only affect the T1/T3 circuits served by the failed network component. Each T1/T3 circuit is treated independently when evaluating the impact of a network component failure on the network performance and when analyzing the network outage, such as FCC reportable incidents (based on the lines affected and duration of the outage). The traditional series-parallel reliability block diagram (RBD) model is usually used to analyze the reliability of an individual T1/T3 circuit. On the other hand, a packet-switched IP network introduces reliability issues that do not arise in circuit-switched networks. For example, in addition to the possibility that connectivity may be lost between the network elements, IP networks can introduce the possibility of induced performance degradation during failure conditions, which consumers may perceive as an outage even when connectivity exists. The impact of these perceived outages may not be limited to consumers served by the failed network elements, but may possibly affect the entire population served by the network.
This invention provides a system and method for reliability evaluation and performance analysis of a backbone network of a large Internet Service Provider (ISP). With given inputs, such as a network topology, the underlying Interior Gateway Protocol (IGP) used, and the traffic matrix collected, a prototype tool, i.e., Network Reliability And Performance (NetRAP), can determine (1) how traffic is routed through the backbone network; (2) which are the congested links in the network; (3) at which interfaces and how many packets are dropped due to congestion or loss of connectivity; (4) the impacts of each single network component failure in terms of packet loss caused by the failure; and (5) how effective is a proposed traffic engineering/capacity planning solution.
By using the input data files in conjunction with the NetRAP apparatus, the NetRAP apparatus is capable of calculating the reliability/performance measurements. The NetRAP apparatus is also capable of listing congested links and identifying critical network components.
The IP network reliability and performance measurements may consist of three parts: 1) accessibility, which is the probability of successfully initiating a transaction into the network; 2) continuity, which is the probability of successfully completing an initiated transaction in the network; and 3) fulfillment, which is the probability that the level of performance in completing a transaction is within acceptable bounds for the provided service, i.e., a quality of service determination.
For an IP backbone network which is bounded at Access Routers (ARs) and Internet Gateway Routers (IGRs), packet transactions start and end at ARs and/or IGRs. Here the packet loss ratio of total incoming packets (TIP) into the network is used as the network reliability/performance measurement. More specifically, the accessibility loss is measured by the packet loss ratio due to disconnection caused by ingress AR/IGR failure. The continuity loss is measured by the packet loss ratio due to disconnection between ingress and egress ARs/IGRs (including the egress AR/IGR failure) under the condition that the ingress AR/IGR is accessible. In addition, the fulfillment is measured by the packet loss ratio due to congestion on interfaces of network links. However, packet loss due to congestion is only part of the fulfillment measurement. Additional measurement for fulfillment such as a packet loss ratio due to network delays (i.e., propagation delay, insertion delay and queuing delay) may also be used.
The present invention concerns a technique for analyzing the performance of an IP backbone network in accordance with the ratio of network packet loss. This loss ratio of the total incoming packets into the network provides a measure of the reliability and performance of the network.
These and other aspects of the invention will be apparent or obvious from the following description.